Team Demonstrates Effective New ‘Biopsy in a Blood Test’ to Detect Cancer

Scientists
from The Scripps Research Institute, Scripps Health, and collaborating cancer
physicians have successfully demonstrated the effectiveness of an advanced
blood test for detecting and analyzing circulating tumor cells (CTCs)—breakaway
cells from patients’ solid tumors—from cancer patients. The findings, reported
in five new papers, show that the highly sensitive blood analysis provides
information that may soon be comparable to that from some types of surgical
biopsies.

“It’s
a next-generation technology,” said Scripps Research Associate Professor Peter
Kuhn, senior investigator of the new studies and primary inventor of the
high-definition blood test. “It significantly boosts our ability to monitor,
predict, and understand cancer progression, including metastasis, which is the
major cause of death for cancer patients.”

The
studies were published February 3, 2012, in the journal Physical Biology.

The
new test, called HD-CTC, labels cells in a patient’s blood sample in a way that
distinguishes possible CTCs from ordinary red and white blood cells. It then
uses a digital microscope and an image-processing algorithm to isolate the
suspect cells with sizes and shapes (“morphologies”) unlike those of healthy
cells. Just as in a surgical biopsy, a pathologist can examine the images of
the suspected CTCs to eliminate false positives and note their morphologies.

Kuhn
emphasizes that this basic setup can be easily modified with different
cell-labeling and image-processing techniques.

Five
New Studies, Five Steps Forward

To
test the new technology, members of the Kuhn lab at Scripps Research teamed up
with pathologists and oncologists at Scripps Health in La Jolla, California; UC
San Diego Moores Cancer Center at the University of California, San Diego; the
Billings Clinic in Billings, Montana; the Division of Medical Oncology at the
University of California, San Francisco; the Center for Applied Molecular
Medicine at the University of Southern California, in Los Angeles; and the
Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital in Amsterdam, the
Netherlands.

The
five new studies that resulted from the collaboration not only demonstrate the
accuracy and effectiveness of the new test for a number of different cancer
types, but also begin to explore the utility of the technology for diagnosing
and monitoring patients and improving cancer research in the lab. While other
tests for CTCs typically use “enrichment” steps in which suspected CTCs are
concentrated—and these methods inadvertently exclude some types of CTCs—the new
studies show HD-CTC works well as a no-cell-left-behind process and enables a
more complete analysis.

Also
striking is the quality of the images. “The high definition method gives a
detailed portrait of these elusive cells that are caught in the act of
spreading around the body,” said diagnostic pathologist Kelly Bethel of Scripps
Health, Scripps Research, and UC San Diego School of Medicine, who is the
senior clinical investigator on Kuhn’s team. “It’s unprecedented—we’ve never
been able to see them routinely and in high definition like this before.”

In
the first study, the research team examined 83 advanced cancer patients using
HD-CTC to document the test’s sensitivity and accuracy for different cancer
types. The scientists found that the test detected five or more CTCs per
milliliter of blood in 80 percent of patients with metastatic prostate cancer,
70 percent of those with metastatic breast cancer, 50 percent of those with
metastatic pancreatic cancer, and no healthy subjects. The current
gold-standard CTC test, known as CellSearch, was notably less sensitive in
detecting tumor cells in these samples.

Most
patients whose CTC counts surpassed the detection threshold also showed small
aggregates of CTCs, which cancer biologists term “microtumor emboli.” These are
widely suspected to be incipient metastatic tumors, as well as triggers for the
blood clots that often kill advanced cancer patients. In the second study, the
scientists showed that HD-CTC could detect these aggregates in 43 percent of 71
patients with advanced prostate, lung, pancreas, and breast cancers, and in
none of a group of 15 healthy subjects. “This tells us that HD-CTC could be
helpful in studying the origins of cancer metastases and related blood clots,
and for predicting them, too,” Kuhn said.

In
the third study, the team used HD-CTC to compare circulating tumor cells from
prostate cancer patients with cells from prostate cancer cell lines that
researchers often use as convenient models for prostate cancer biology in the
lab. The team found significant differences between the two classes of cells,
in their cell morphology and in the way they were labeled by HD-CTC’s
fluorescent tags. “This underscores the need for studying cancer cells from
patients, not just model cancer cells that in some ways may be utterly
different from the real thing,” Kuhn said.

In
the fourth study, the researchers performed HD-CTC tests on 28 patients with
advanced non-small-cell lung cancer over periods of up to a year. The team was
able to detect CTCs in 68 percent of samples, and found that the numbers of
detected CTCs tended to go up as other measures showed cancer progression.

In
the fifth and final paper of the series, the team used HD-CTC in 78 patients
who had just been diagnosed with various stages of non-small-cell lung cancer.
“We demonstrated that we could sensitively detect CTCs even in patients with
early-stage cancer,” Kuhn said.

This
result points to the possibility of using the HD-CTC blood test not only to
evaluate already-diagnosed cancer, but also to help detect cancer in people who
are unaware they have it. “If HD-CTC works on the day after cancer diagnosis,
as we’ve shown, then one can easily imagine that it would work the day before
diagnosis, too,” Kuhn said.

Kuhn
and his colleagues now intend to study the use of HD-CTC as a potential
screening test and to develop it further for use in clinical monitoring and
cancer research. Kuhn has founded a San Diego-based biotechnology company, Epic
Sciences, Inc., to develop HD-CTC commercially for companion diagnostic
products in personalized cancer care.

Dena
Marrinucci of Scripps Research was first author of the study, “Fluid biopsy in
patients with metastatic prostate, pancreatic and breast cancer”; Edward H. Cho
of Scripps Research was first author of “Characterization of circulating tumor
cell aggregates identified in patients with epithelial tumors”; Daniel C. Lazar
of Scripps Research was first author of “Cytometric comparisons between
circulating tumor cells from prostate cancer patients and the
prostate-tumor-derived LNCaP cell Line”; Jorge Nieva of Scripps Research was
first author of “High-definition imaging of circulating tumor cells and
associated cellular events in non-small cell lung cancer patients: a longitudinal
analysis; and Marco Wendel of Scripps Research and Lyudmila Bazhenova of UC San
Diego Moores Cancer Center were first authors of “Fluid biopsy for circulating
tumor cell identification in patients with early and late stage non-small cell
lung cancer; a glimpse into lung cancer biology.” For more information on the
papers, see http://iopscience.iop.org/1478-3975/

Kuhn’s
laboratory is supported by the National Cancer Institute (NCI) of the US
National Institutes of Health as the NCI Scripps Physics Oncology Center, which
was initially supported through the American Recovery and Reinvestment Act. For
more information see http://4db.us and http://physics.cancer.gov.

Scripps Research Institute Associate Professor Peter Kuhn (right) worked with physicians including Kelly Bethel of Scripps Health to demonstrate the effectiveness of an advanced blood test for detecting and analyzing circulating tumor cells. (Photo by Dave Freeman.)